Appendix K. List of Reserved Words

Table of Contents
List of Keywords
Predefined Variables
Predefined Classes
Predefined Constants

The following is a listing of predefined identifiers in PHP. None of the identifiers listed here should be used as identifiers in any of your scripts. These lists include keywords and predefined variable, constant, and class names. These lists are neither exhaustive or complete.

List of Keywords

These words have special meaning in PHP. Some of them represent things which look like functions, some look like constants, and so on--but they're not, really: they are language constructs. You cannot use any of the following words as constants, class names, function or method names. Using them as variable names is generally OK, but could lead to confusion.

Table K-1. PHP Keywords

and	or	xor	__FILE__	exception (PHP 5)
__LINE__	array()	as	break	case
class	const	continue	declare	default
die()	do	echo()	else	elseif
empty()	enddeclare	endfor	endforeach	endif
endswitch	endwhile	eval()	exit()	extends
for	foreach	function	global	if
include()	include_once()	isset()	list()	new
print()	require()	require_once()	return()	static
switch	unset()	use	var	while
__FUNCTION__	__CLASS__	__METHOD__	final (PHP 5)	php_user_filter (PHP 5)
interface (PHP 5)	implements (PHP 5)	extends	public (PHP 5)	private (PHP 5)
protected (PHP 5)	abstract (PHP 5)	clone (PHP 5)	try (PHP 5)	catch (PHP 5)
throw (PHP 5)	cfunction (PHP 4 only)	old_function (PHP 4 only)	this (PHP 5 only)